Self-assembled ferric oxyhydroxide nanosheet on PEO-coated magnesium alloy with photocatalytic/photothermal antibacterial and enhanced osteogenesis activities

• Bio-functional FeOOH nanosheet-engineered Mg-based bone implants were developed. • FeOOH film was safe and improved Mg implant corrosion resistance/biocompatibility. • FeOOH film showed superior photocatalytic/photothermal effects. • The Mg-based implants had bactericidal and bone defect regenerating properties. Bone implants with excellent antibacterial and osteogenic activity are beneficial in decreasing the risk of infection and accelerating the healing of injured bone tissue. Biodegradable Mg alloys are considered promising new platforms for treating bone-related diseases. However, the shortcomings of these alloys, including rapid corrosion and insufficient bio-functions (antibacteria and osteogenesis) severely limit their widespread applications. In the present work, ferric oxyhydroxide (FeOOH) nanosheets were grown in situ on plasma electrolytic oxidation (PEO)-coated Mg alloy through a simple and green immersion treatment. The highly-oriented FeOOH nanosheets completely sealed the porous structure of the PEO coating, and thereby significantly improved the corrosion resistance and biocompatibility of the Mg alloy. The prepared FeOOH films provided antibacterial activity through two modes. (i) the first is a photocatalytic effect, which prevents infections or contamination during storage and transportation and can be used to quickly sterilize the implants under sunlight before implantation into the human body. (ii) The second is a photothermal antibacterial effect, which has been shown to effectively kill Staphylococcus aureus that adhered to implants placed under the skin of mice using near infrared (NIR) light. Moreover, the enhanced corrosion resistance and synergistic biofunctions of the Mg and Fe ions of the FeOOH nanosheet-reinforced Mg alloy implants significantly facilitated cell adhesion, spreading, and proliferation and accelerated osteogenesis.